Pneumatic counterbalance having a control mechanism therefor



Aug. 25, 1959 E. F. sPElDr-:N 2,900,841

PNEUMATIC COUNTERBALANCE HAVING A CONTROL MECHANISM THEREFOR Filed oct. zo. 195s 6 Sheets-Sheet 1 EDGAR F SPE/.DEN

i ATTORNEY Aug. 25, 1959 E. F. sPElDEN 2,900,841

Prmulvm'rrc COUNTERBALANCE HAVING A CONTROL MECHANISM THEREFOR Filed oct. 20. 1953 l e sheets-sheet 2 "MMM Emu: I

I l l E Illlll/lllfll/ll INVENTOR 506A@ F .SPE/DEN IIIlIIl/IIIIIIIII ATTORNEY Aug. 25, 1959 E. F; sPElDEN 2,900,841

PNEUMATIC COUNTERBALANCE HAVING A CONTROL MECHANISM THEREFOR Filed Oct. 20, 1953 Y 6 Sheets-Sheet 3 ATTORNEY Aug. 25, 1959 E. F. sPElDl-:N 4 2,900,841

PNEUMATIC COUNTERBALANCE HAVING uA CONTROL MECHANISM THEREFOR Filed oct. 2o. 1953 e sheets-snaai 4 1N VENTOR 5 3F27 ATTORNEY Aug. 25, 1959 E. F. sPElDEN 2,900,841

PNEUMATIC COUNTERBALANCE HAVING A CONTROL MECHANISM THEREFOR Filed Oct. 20, 1953 6 Sheets-Sheet 5 ABY ATTORNEY Aug. 25, 1959 2,900,841

PNEUMATIC COUNTERBALANCE HAVING A CONTROL MECHANISM THEREFOR Filed Oct. 20, 1955 E. F. SPEIDEN 6 Sheets-Sheet INVENTOR 506A E F SPE/DEN ATTORNEY nitedI States Patent M PNEUMArrc coUNrEALANcE nAvnsrG` Aa coNrRoL ivlnscnmsnsM` THEREFOR Edgar F. Speitiern Parkersburg, W. Va., `assignor to The Parkersburg Rig & Rel Company, Parkersburg, W. Vai,` a corporation ofWestVirginaA Application October 20, `19S3,Serial No. 387,261 1s1 Claims. (clim-:swr

to store .energy on the down stroke of the `rods land -to expend energyon the up stroke, as is well known. In one type of 'such unit in common operation,` the .capacity of the air forcounterbalancing purposes is substantially increased by the use of a receiver communicating with the pressure chamber of the counterbalance. Such re ceiver is provided with a manually operable cut-ofvalve tretain air under pressure in the receiver when the pumping rig is shut down for any purpose, for example,- for servicing.

It is not unusual for operators to neglect 4to close the cut-olf valve when shutting downxa unit.` Neither i`s` it" unusualffor'` the prime mover:on the unit toV stop due to power failure or othercause when no one is` presentkto' close the shut-off valve. In either case, so much air may escape from the system that'considerable additional Work is required to start the` unitllback in.` normal operationL When the prime mover is an electric moto'r, it isV not uncommon to have the Vunit operatelon a cycle ofso many hours of-pumping andso many hours idle.V Such" units are usually. controlled by atime'clock.

Insother motor-driven units, `theoperating cycle Tmayi` require several days of pumping.` and several days idle, and such units -may` be operated fromfaremo'tecontrolA station.4 In bothl` cases, there may be no `one .present stopped or. started. A

r When,- after a shutado'wn ofhthe unitfor any cause,

y theair pressure drops `so low as not to4 permit thethe .unit isf shut down, totretain air under pressure" in the receiver, thus facilitating the restarting of-'the^unit.

Afurther object is to provide such a system ,wherein-`r thefautom'atc `control means is responsive"` directly or indirectly to the operation of the prime mover so asto immediately close communication between the receiver" andn the counterbalanceiunit whenever theprimemover ceases operation. A

A further Vobject is toprovide anove1'control'valve" 70 for controlling communication between the= receiver and" thetcounterbalance r uni-tA and wherein the-control i valve Patented Aug'.` 25, .1959-- 2 is".biased to open position to remain in such `position during normal operation of the unit, and to provide automatic means, `operable whenever the pumpingunit ceases operation, to 4overcome the biasing means of the controly valve and close such valve to disconnect the receiver from the counterbalance unit. r

A further object is to provide such a system whereinpressure in the receiver is utilized at least partially as thelbiasingmeans tending to open the control valve when the unit is started` in operation, and wherein the same pressure is utilized automatically when .the counterbalance ceases to operate, to close the control valve for the purpose stated. A

A further object is to provideV such a system wherein the control means lendsitself readily to operation by any type of huid under pressurelsuch` as hydraulic pressure, whenV the prime mover is an internal combustion.` engine, 4and to air pressure `controlled by a solenoid valve, when the prime mover an electric motor. A

AOther objects and advantages of the invention will V become apparent during the course of the following 1de` s cription.

r In ythe drawings I `have shown two embodiments -of' the invention. In this showing:

Figure 1 is a side elevation of a pneumatically counterbalanced walkinglbeam showing the invention applied;y r Figure 2 is .anenlarged-fragmentary elevation shoW- Ilga portonlof l the receiver and the control valvev mechanism therefor and associated elements, looking from the right-hand sidel of the receiver in Figure 1;`

Figure 3 is a Vgenerally similar view showing the parts diagrammatically and4 including the counterbalance unit with vthe cylinder thereof shown in section;

Figure 4is a side elevationof the hydraulic reservoir and-associated elements used in one form of the invention; r

Figure 5 is .an enlarged sectional view of the control or- 4cut-olf valve, `parts` being shownin elevation;

Figure is a transverse sectional view on line 66 of Figure 5; .l r

Figure 7 is an enlarged axial sectional View through the Vrelay valve device `for operating the control valve;

Figure Sis a section on liners-8 of Figure 7;

Figure 9 is an enlarged sectional view through a pressure relief valve;

Figure 10 `is Va section on line 10-10 of Figure 9; and

Figure l1 is a diagrammatic view of a modified type of system utilizing a solenoid valve in conjunction with the relay valve.

Referring to Figure 1, there is illustrated a pneumatif cally counterbalanced pumping unit comprising a base 10 on which is mounted the usual Samson post 11 pivotally connected as at 12 to a walking beamV 13. This beam carries the usual head 14 connected through a suitable cablelS with conventional polished rods (not shown) of the `oil well.

A conventional prime mover 16, which may be of any desired type, operates through a belt or chain 17 to drive a conventional speed reducing unit 18 having` an output shaft `19, to whichis connected a crank 2t).

A-crank pin21 pivotally connects the crank to a pitman 22 Ahaving `pivotal connection as at 23 with the walking beam to oscillate the latter in a verticalplane on thef rod 29""shwn"only"diagrarnmatically in Figure 3 and1 pivotally connected at its lower end as at 30 (Figure 1) to the base in accordance with conventional practice. The piston 28 and cylinder 26 denne a pressure chamber 32 which expands upon upward swinging movement of the walking beam and is contracted upon downward movement of ythe beam to place air in the chamber 32 under increasing pressure to store energy under such conditions. The piston rod 2.9 is hollow to provide therethrough a passage 33 communicating at its upper end with the chamber 32 and at its lower end with a pipe or conduit 34 leading in a manner to be described to a receiver 36. As thus far described, the pneumatic counterbalancing system ris conventional, and in the usual practice, cornmunication between the pipe 34 and receiver 36 is controlled by a manually operated cutoil valve. ln accordance with the present invention, this communication is controlled by an automatic valve indicated as a whole by the numeral 37 and described in detail below.

In accordance with conventional practice, the valve 37 is open when the pumping unit is in operation, and the average air pressure in the system throughout each cycle of walking beam operation is that required to exert an upward pressure against the walkingrbeam equal to the weight of the pump rods plus one half the weight of the fluid column above the plunger of the well pump.

Other accessory devices are associated with the pumping unit such as a compressor 38 (Figure l), an intermediate air receiver, etc. These accessory devices have not been particularly illustrated since they may be of any operative type and form no part per se of the present invention. For the purpose of illustration, the pipe 34 has been shown in Figure 3 as leading directly from the tubular piston rod 33 to the valve 37 and thence to the main receiver 36.

The control or cut-off valve has been illustrated in detail in Figure 5. This valve is a complete operative mechanism and comprises a valve housing 42. having a valve seat 43 therein controlling communication between the central portion of the valve housing 42 and the receiver 36 through a pipe d4. The other end of the valve housing 42 is connected by a union 45 to a bearing member 46 in which is slidable a rod 47. This rod carries a valve body e8 to which is connected a valve 49' engageable with the seat 43 upon movement of the rod 47 toward the seat 43 in a manner to be described. The valve body 48 preferably moves in a suitable valve guide 50. The pipe 34 communicates with the central chamber 51 of the valve housing 42 as shown in Figure 5.

The bearing 46 has an extended apertured sleeve portion 54 carrying a plate 55 .to which is secured by screws 56 one housing 57 of a diaphragm device, the other housing of which is indicated at 58. These housing members are secured together by bolts 59 and clamped therebetween is lthe peripheral portion of a diaphragm 60 of any suitable ilexible material. A bearing plate 61 attached to the diaphragm carries a stem 62 fixed to the adjacent end of the stem 47 in axial alinement therewith. A spring 63 biases the diaphragm 60 to a position in which the valve 49 is open. This spring is arranged in the chamber 64 of the casing member 57 which communicatcs with the atmosphere through the apertures of the sleeve member 54. The chamber 65 of the casing member 58 has communication with a pipe 66 for a purpose to be described.

in Figures 7 and 8 there is illustrated a relay valve for controlling pressures in the diaphragm chamber l65. The relay valve is indicated as a whole by the numeral 70 and comprises upper and lower casing members 71 and 72 respectively having hanged adjacent ends secured together by screws 73 with an interposed valve seat unit 74 therebetween. T he latter member, together with the casing member 71, delines a chamber 75 in constant communication with a pipe 76, connected to the pipe 66, and such connection therein having a manually operable bleed valve 77 (Figure 3) for releasing air pressure in the diaphragm chamber 65 when desirable. Another pipe 78 (Figure 7) communicates with the chamber 75 through a valve seat 79 further referred to below.

A piston 82 is slidable in the housing 72, which is of cylindrical form, and includes a lipped cup 83 of deformable material to provide an effective seal between a chamber 84 below the piston 83 and a chamber 85 above this piston. The latter chamber is adapted to communicate with the chamber through a passage 86 in the valve seat unit 74, and the upper end of the passage 86 terminates in a valve seat 87.

Fluid under pressure is supplied to the chamber 84 in ways to be described, only when the pump-ing unit is in operation. When such pressure is present, the piston 82 is urged upwardly against the tension of compression spring 88, and this spring moves the piston 82 downwardly when pressure ceases to exist in the chamber e4 incident to the shutting down of the pumping unit.

A stem 90 is connected at its lower end to the piston 82. This stem projects loosely through the passage 86 and carries at its upper end a valve body 91 having upper and lower valve elements 92 and 93 respectively engageable with the seats 79 and 87. When no pressure is present in the chamber 8d, the pipes 76 and 78 communicate with each other and the chambers 75 and 85 arev disconnected by valve element 93. When the pumping unit is operating and pressure is present in the chamber Se, the valve element 92 engages the seat 79, thus disconnecting pipes 76 and 78 from each other and establishing communication'between the pipe 76 and chamber 85, the valve 93 then being open. The chamber 85 is vented to the atmosphere as at 94. Under the conditions referred to, therefore, atmospheric pressure will be established in the pipe 76 and hence in the diaphragm chamber 65 (Figure 5).

Referring to Figure 3, it will be noted that a pipe 96 is tapped at one end into the pipe 44 and at its other end into the pipe 34 with a check valve 97 interposed therein. The pipe 96 provides a bypass around the valve 37 and, with the check valve 97, comprises a safety means to prevent rupture of the piping between the counterbalance and the valve 37 in the event the valve 49 (Figure 5) closes while the pumping unit is still in operation.

One end of the pipe 78 (Figure 3) is tapped into the pipe 96 between the check valve 97 and pipe 44, and in the pipe 78 is interposed `a pressure regulating valve 98. Accordingly, while air from the receiver 36 is connectedV to the pipe 78 leading to the relay valve chamber 75, the air pressure in this chamber is regulated and will be substantially below pressures in the receiver 36.

Two types of means are illustrated for establishing pressure in the chamber 84 (Figure 7) while the pumping unit is in operation. The high speed shaft 100 of the speed reducing unit 18 drives a belt 10.1 passing around a pulley 102 for thus driving a pump 103 (Figures 2 and 3), preferably of the hydraulic type. This pump has its intake side connected as at 104 to a hydraulic fluid reservoir 105 and the outlet side of the pump is connected to a pipe K106 having a T 107 preferably provided with a pressure gage 108. The run of the T is connected respectively to a pipe 109 leading to the relay Valve chamber 84 (Figure 7) and to a pipe `110 which communicates with a relief valve 111 shown in detail in Figures 9 and 10.

The relief valve 111 comprises a valve body 112 having a bore 113 therein communicating through a pipe 114 (Figures 3 and 9) with the reservoir 105. A valve 115 is mounted in the bore 113 and is square or otherwise rectangular in cross section to provide channels 116 through which hydraulic iluid can ow from pipe 110 to pipe 114 under conditions which will become apparent. The valve is provided with a conical end valve face 117 engageable with a similarly shaped valve seat 118. The end of the valve 115 is provided with a transverse slot 119 which affords restricted communication between the pipe 110 and the bore i113 when the valve face 117 is seated.

A springgZl urges the valve,.115 towardelosed .position andv is backed up preferably by a plurality of adjusting: plugs 122 "followed by a cljsure plug 123.` The plugs 122 may be adjusted and different springs 121 .employed to predetermine the pressure at..which ithe `valve 115 opens. p

It will be apparent that the pump 103 is. driven con-` stantly whenever the pumpingunit is in operation, thusV supplying hydraulic pressure to the relay valve chamber. '84T Excess hydraulic fluid will be bypassedthrough pipe 110 Tand relief valve 111 to the reservoir 105. l

Thepump 103, reservoir 105 and associated elements may be dispensed with if the prime mover is anelectric` motor. Under such conditions, vthe relay valve device willVbe-controlled in the manner shown in Figurell. Under such conditions, the pipe 78 will beconnectedto the relayvalve chamber 75 through a T'-128,.and the run ofthis T is` connected through a pipe 12"9ftothe.y

housing 130 'of a solenoid valve indicated as a whole byn the numeral 131. A valve 132 is arranged in the housing 130 "and is biased downwardly by any. suitable, means (not shown), and is movable to the upper position shown in' Figure 11 upon energization of la solenoid .133. For the purpose of illustration, this solenoid is shown asbeing connected in series with the motor 134 forming the prime mover of the pumping unit. However, any.suit`able` circuit`control means may be provided for the solenoid toenergize it whenever the prime mover isA operating, thus-` maintaining lthe valve 132 fin the position shown in Fig"- ure 11`.`

The valve 132 is`provided with'a through passage 13'6 alined with the pipe 129 when the solenoid'133 `is enerf gized, thus connecting this pipe tota pipe 137"1e`adin`g`to the relay valve chamber 84 inV place of the pipe 109 prev-iously described. Whenever the pumping unit is" in op-` eration, therefore, the valve element 92 (Figure 7) willbe closed and the pipe 76 will be exhausted to the atmos phere, thus maintaining atmospheric pressure in the diafphragm chamber 65 (Figure 5).`

The valve 132 further comprises a `transverse port`140u communicating at one side of the valve with the port 136 through a longitudinal passage 141'. This passage eX- tends above the port 136 to communicate with`the pipe 137 when the valve 132 drops upon de`energization of the" solenoid 133." Under suchconditions, the pipe 129"will` be cut off from the passage 136'and` the'pipe 137 will communicate with an exhaust pipe 142 preferably provided with a manually operable valve 143 for controlling y the rate of exhaustion of `air from the relay valve chamf ber `84 for a purpose to bede'scribed.`

Operation .shown infFigure 1 operates inthe conventional manner,

the walking beam 13 oscillating about the axisof the pivot 12 to effect reciprocation `of the well rods; power being delivered from the prime mover 16 through the speed `reducing unit 18,crank 20, Vand pitman I22. The pump 103* will 'be'tconstantly drivenI and will maintain-pressure in the rrelay `valve chamber 84 to hold the-piston'82 in its upper dotted 'line position shown in Figure 7 t The valveA element92 will remain `engaged with the seat 79 and the piper78 (Figures 2 and 3) will'be closed to communica#A tion `with the pipe 76. This pipe, which isin fixed com-l munication with the diaphragm chamber 65 through pipe` 66,7will betopen to the atmosphere through chamber 75,n passage 86; chamber 85`, and ventopenings94. Accord` ingly, the `chamber 65 (Figure 5) will be under `atmospheric pressure, and the spring 63 will maintain the valve t 49 open. Thus, thepipe 44,1leadingto the receiver 36,. will be in open communication with the pipe 34 and there-z fore in communication withthe counterbalance chamberV 32 through the hollow piston rod 33. Accordingly, the necessary volume of air u nder pressure for counterbalancing .the pumpingeunit` will be present to `be. utilizedgin the usual manner. Energy will beustored upon down4 ward movement of the vwalking beam 13 and will be expended upon the `up strokeof the pump rods to counterbalancethe pumping action. p v

Aspreviously stated, the valve 37 is substituted for the conventional manual cut-ofi` valve. Such valve vis operated in conventional units of this type whenever the pumping unitis shut down. However, the operator sometimes forgets to shut the'valve, and if he shuts it, he often forgets to open the valve whenthe unit is restarted. Under the latter condition, the compressor 38 (Figure l). will operate to build up its intended pressure, but the volume of air present under pressure obviously is not sufficient for counterbalancing purposes. If pressure is lost from the receiver 36, it is necessary to uncouple the pump rodsfrom the walking beam, operate-the beam to restore the necessary quantity of air under pressure,` and then shut down the unitV and recouple the pump rods before restoring the normal operation. This entails a conisderable amount of work and lost time.

With `the present system, the stoppingfof the prime mover 16 stops the pump 103 which no longer operates to generate pressure in the relay valve chamber 84 (Figure 7). The relief valve 111 (Figure 9) then comes into operation to provide leakage from the outlet side ofthe pump `through the slot119 into the bore 113 and thence into the reservoir 105 through pipe 114. This will result in a somewhat delayed relieving of the pressure in the diaphragm chamber 84, thus preventing the sudden dropping of the valve body 91 and momentarily preventing communication between pipes 76 and 78. This protects thefpiping of the apparatus when the rotating parts turn over several times after power `of the prime mover has been cut olf, for a purpose which will become apparent.

When pressure drops to the necessary extent in the relay valve ychamber 84,- the spring- 88 will move the piston 82 downwardly, thus opening the valve 92 and closing the valve 93. The chamber will now be cutl off from the. atmosphere, and pipes 76 and 78 will communicate with each other. Referring to Figures 3 and 5, it will be apparent that under such conditions air will7 flow from pipe 78 through Apipes 76 and 66 into the diaphragm chamber 65. Due to theuse of the pressure reducing valve 98, air under pressure supplied tothe chamber65 will bebelow any pressures existing. in the receiver 36. However, the diaphragm` 60 is of substantial area and the `total pressure thereagainst over` comes the spring 63 to move the valve 49 lto closed position, the pressure affecting the diaphragm 60` likewise being. sufficient to overcomereceiver pressures inpipe 44 `tending to prevent the seating of the valve49.

From the foregoing, it will be apparent that fluid pressure is utilized to maintain the valve 49 closed' whenever `the `pumping unit is` not in operation, and, most practicably, this fluid pressure is-derived from the receiver 36 itself. The valve49 is maintained seated under pressure and prevents any leakage between pipes 34 and 44. Accordingly, thetapparatus may remainout of operation for substantial periods of time without lo'ss'- of pressure from the receiver 36.

When the pumping operation is'to be'restored, itis necessary merely to start the prime mover 16. The walking beam operation will then commence and the hydraulic pump 103 will immediately function and, almost instantly, pump the amount of `hydraulic fluid necessary t to overcome the tensionof the spring 8S (Figure 7).1 The piston 82, accordingly, will be moved upwardly` to very quickly open the `valve 93 and close the valve 92. The diaphragm chamber 65 immediately will be cut off from communication with the pipe 78 and will be openeduy to the atmosphere through chamber 75, passage 86,` etc;l Promptly upon the starting of `the prime mover,therefo're,\V the chamber 65 will be relieved `of pressuretand the spring 63, assisted by receiver pressure acting directly@` 7 on the valve 49, will move this valve to open position and connect pipes 34 and The large volume of air under pressure in the receiver, accordingly, will be rendered available to the counterbalance unit, and operation of the pumping unit will be restored without loss of time and the expenditure of labor, as described above.

The valve 111 (Figures 9 and l0) is primarily a pressure relief valve. it will be apparent that the pump 103 operates continuously, and as soon as the necessary hydraulic fluid under pressure has been displaced to the relay valve chamber 84 to close the valve 92, the pumped hydraulic uid must be taken care of. Under such conditions, the valve 115 is pushed under pressure from the seat E118 to permit the flow of hydraulic fluid back to the reservoir MD through pipe 1M (Figures `3 and 9). By adjusting the set screws i122 and changing the compression of the spring 121, the discharge pressure of the pump 103 may be adjusted.

The operation of the form of the invention 'shown in Figure ll is similar to that previously described. The same relay valve device 70 may be employed, and this device is shown in the diagrammatic representation in Figure ll. Instead of supplying liquid from a hydraulic pump (or air from a compressor) to the chamber 84 to move the piston 82 upwardly, air from the receiver 36 is used for this purpose. So long as the pumping unit is in operation, the valve 132 will be in the position shown in Figure 11 through energization of the solenoid 133. The pipe 78 thus will remain in communication with the pipe 137 to supply air under pressure to the chamber 8d to maintain the valve 92 (Figure 7) closed and the valve 93 open, thus maintaining the diaphragm chamber 6d (Figure 5) open to the atmosphere.

Assuming that the prime mover i3@ is stopped, the circuit through the solenoid E33 will be opened and the valve 132 will drop to its lower position. The passage 136 will be moved out of registration with the pipe 129, and the pipe 3.37 will be connected to the atmosphere through passages Ml and 14d, pipe i242 and valve 143. The relay valve chamber 81% thus will be connected to the atmosphere and the valve body 9i will drop to the solid-line position shown in Figure 7 to connect pipes 76 and 7S. Thus, air under pressure will be supplied as before t0 the diaphragm chamber 65 to close the valve 49.

It is desirable, as previously stated, to slightly retard opening movement of the valve 92 to allow time for the pumping unit to come to rest. ri`his .voids supplying eX- cessive pressure to pipe 3ft if the valve 37 is closed. The closing of this valve is slightly delayed by adjusting the valve 143 (Figure l1) to retard the rate of exhaustion of air pressure from the relay valve chamber 84 to the atmosphere, thus accomplishing the same result as the slot 119 shown in Figure 9.

The use of either of the systems referred to, therefore, is highly advantageous in preventing possible damage to the apparatus through failure of an attendant to open the usual cut-ofi valve connecting the receiver to the counterbalance unit when operation of the pumping unit is restarted. The system also prevents the loss of pressure Ifrom the receiver automatically whenever Vthe prime mover of the pumping unit is stopped and immediately and automatically renders available a large volume of compressed air when the pumping unit is restarted. It is therefore unnecessary for an attendant to perform any function other than the stopping of the prime mover, provided an attendants services are utilized for this purpose. Gbviously, the functioning of the prime mover may be subject to remote control so that the pumping unit may be started in operation whenever desired, maintained in operation for any period of time, and then stopped. Moreover, the prime mover may be again started in operation by remote control without the necessity for the performance of any service by an attendant. Y

It is to be understood that the forms of the invention illustrated and described .are illustrative only, and that the invention is defined in the appended claims.

I claim:

1. A counterbalancing apparatus for a pumpingrunit having a prime mover and a walking beam driven thereby and constituting therewith a continuously operable mechanism, comprising a pneumatic counterbalance connected between the walking beam and a stationary support, a pressure receiver communicating with said counterbalance, a valve controlling such communication,

means biasing said valve to normally open position to maintain communication between said receiver and said counterbalance, a casing having a pressure responsive element therein connected to said valve and defining with said pressure responsive element a pressure chamber, a conduit connected between said chamber and said receiver, a relay valve in said conduit biased to open piping position, and means operative only during operation of said continuously operable mechanism for maintaining said relay valve closed whereby such valve automatically opens to supply pressure fluid from said receiver to said chamber to move said pressure responsive element against said biasing means to close said first-named valve when operation of said walking beam is stopped.

2. A counterbalancing apparatus for a pumping unit having a prime mover and a walking beam driven thereby and constituting therewith a continuously operable mechanism, comprising a pneumatic counterbalance connected between the walking beam and a stationary support, a pressure receiver, a conduit connecting said receiver to said counterbalance to increase the volume of pressure Huid available for said counterbalance, a valve in said conduit controlling communication therethrough and biased to normally open position, a diaphragm housing, a diaphragm therein connected to said valve and forming with `said housing a pressure chamber,

- piping connecting said receiver to said pressure chamber,

a relay valve controlling said piping .and biased to an open piping position, iiuid pressure responsive means for moving said relay valve to closed position to trap pressure fluid in said receiver and exhaust said pressure chamber to the atmosphere, and means dependent upon operation of said continuously operable mechanism for subjecting said pressure responsive means to pressure Huid to maintain said relay valve closed.

3. Apparatus constructed in accordance with claim 2 provided with a control chamber to which pressure Huid is admitted to control said relay valve, and means for retarding the exhaustion of pressure Huid from said control chamber when the operation of said continuously operable mechanism is stopped.

4. Apparatus constructed in accordance with claim 2 wherein the means for supplying pressure fluid to operate said pressure responsive means comprises a pump operated by said continuously operable mechanism.

5. A counterbalancing apparatus for a pumping unit having a prime mover and a walking beam driven thereby and constituting therewith a continuously operable mechanism, comprising a uid system including a counterbalance connected between the walking beam and the stationary support, a pressure receiver and a conduit connecting said receiver to said counterbalance to increase the volume of pressure duid available to the latter, a valve in said conduit, a pressure operable unit comprising a casing and a pressure responsive element therein connected to said valve .and dening with said casing a pressure chamber, piping connected between said fluid system and said chamber, a relay valve in said piping biased to one position to connect said uid system with said chamber, said relay valve being movable to .a second position to trap pressure fluid in said duid system and to open said pressure chamber to the atmosphere, a pressure operable device having a housing and a pressure responsive unit therein connected to said relay valve and aeodeai forming with said housing a control chamber, `and means subject to operation only so long as said continuously operable mechanism is operating to supply pressure to said control chamber to maintain said relay valve in said one position.

6. Apparatus constructed in accordance with claim wherein said means comprises a pump driven by said continuously operable mechanism.

7. Apparatus constructed in accordance with claim S provided with means for controlling the releasing of pressure from said control chamber when operation of said continuously operable mechanism is stopped to delay movement of said relay valve away from said one position.

8. Apparatus constructed in accordance with claim 5 wherein said means comprises an auxiliary conduit connected between said piping and said control chamber, an auxiliary valve in said auxiliary conduit and biased-to a position opening said auxiliary conduit to the atmosphere and closing it to said piping, and means subject to operation as long as said continuously operable mechanism is in operation for holding said auxiliary valve in a second position cutting off communication between said auxiliary conduit and the atmosphere and opening such conduit to said piping.

9, Apparatus constructed in accordance with claim 5 wherein said means comprises an auxiliary conduit connected between said piping and said control chamber, an auxiliary valve in said auxiliary conduit and biased to a position opening said auxiliary conduit to the atmosphere and closing it to said piping, means subject to operation as long as said continuously operable mechanism is in operation for holding said auxiliary valve in a second position cutting off communication between said auxiliary conduit and the atmosphere and opening such conduit to said piping, and a manually operable valve connected to said auxiliary valve and operative when the latter connects said control chamber to the atmosphere to control the rate of exhaustion of pressure fluid from said control chamber.

10. A counterbalancing apparatus for a pumping unit having a prime mover and a walking beam driven thereby and constituting therewith a continuously operable mechanism, comprising a pressure system including a counterbalance connected between the walking beam and a stationary support, a pressure receiver, a conduit connecting said pressure receiver to said counter-balance, and means operable by the walking beam for maintaining pressure in said system during operation of the walking beam, a normally open valve controlling said conduit, pressure responsive means comprising a control chamber into which fluid pressure is admissible to close said valve, piping connecting said system to said chamber, a relay valve device having a rst valve seat in said piping, a relay chamber in which said valve seat is arranged and having a second seat opposite said rst valve seat controlling communication between said relay chamber and the atmosphere, a relay valve biased into engagement with said second valve seat to open communication through said piping during operation of the walking beam, said relay. valve being movable to engage the rst valve seat to trap pressure in said system and open said control chamber to the atmosphere through said second valve seat, a pressure responsive unit connected to said relay valve, and means dependent upon operation of said continuously operable mechanism for supplying pressure to said pressure responsive unit to maintain said valve in engagement with said rst valve seat.

11. Apparatus constructed in accordance with claim 10 wherein said means for supplying pressure to said pressure responsive unit comprises a plump driven by said prime mover to be operative only when said continuously operable mechanism is in operation.

12. Apparatus constructed in accordance with claim 10 wherein said means for supplying pressure to said pressure responsive unit comprises a pump driven by said prime mover to be operative only whensaid continuously operable mechanism is in operation, and means providing for retarded ilow of pressure fluid from said pressure responsive unit when operation of said pump is stopped to delay movement of said relay valve away from said rst valve seat.

13. Apparatus constructed in accordance with claim 19 wherein said means for supplying pressure to said pressure responsive unit comprises a hydraulic pump driven by said prime mover and having its outlet connected to said pressure responsive unit, a reservoir, and flow means conecting the outlet of said pump to said reservoir, said flow means having a ow restricting device therein.

14. Apparatus constructed in accordance with claim 10 wherein said means for supplying pressure to said pres- Asure responsive unit comprises a hydraulic pump driven by said prime mover and having its outlet connected to said pressure responsive unit, a reservoir, a pipe connection between the outlet of said pump and said reservoir, and flow control means in said pipe conection, such means comprising a casing having a valve seat therein, a ilow control valve biased into engagement with such seat and seating toward the outlet of said pump, said ilow control valve having a groove affording restricted communication between said pump and said reservoir when such valve is closed, and being movable from its seat to relieve excess hydraulic pump pressures.

15. Apparatus constructed in accordance with claim 10 provided with an electric motor comprising said prime mover, the means for controlling the supplying of pressure to said pressure responsive unit comprising a pipe connection between said pressure system and said pressure responsive unit, a three-way valve in said pipe con- 4nection biased to a position opening said pipe connection to the atmosphere and closing it to said pressure system, and a solenoid subject to energization when said electric motor is energized for moving said three-way valve to a second position cutting off communication between said pipe connection and the atmosphere and opening said pipe connection to said pressure system.

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